There is an active interest in the production of industrial feedstock chemicals or fuels from biomass. Starch is a major component of agricultural crops and of corn processing waste and it is a preferred substrate for chemical and enzyme production because of its chemical composition and its higher density than other forms of biomass which facilitates prolonged storage, and decreases transportation and pretreatment costs.
Starch is known to be a valuable starting material for the enzymatic production of sugar, such as glucose, which may be converted by yeast to ethanol. The main amylolytic or starch converting enzymes used for the industrial production of glucose, maltose and maltosaccharide from starch are .alpha.-amylase, .beta.-amylase, glucoamylase and pullulanase.
The known amylolytic enzymes, except for bacterial .alpha.-amylases, are unstable at the elevated temperatures preferred for the industrial conversion of starch.
It would be desirable to have both a method for the direct bioconversion of starch into ethanol and production of thermostable starch converting enzymes which could be used at the elevated temperature preferred by industry.